[v6.1] general protection fault in __ext4_journal_get_write_access (5)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: f2ddafa93a25 Linux 6.1.166
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=15ebfb5a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f0605c5af04d7603
dashboard link: https://syzkaller.appspot.com/bug?extid=0aec858fdcb9a4d6113d
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/5d86a86f0032/disk-f2ddafa9.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/aafc10ea040b/vmlinux-f2ddafa9.xz
kernel image: https://storage.googleapis.com/syzbot-assets/f6b46858e7a5/bzImage-f2ddafa9.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+0aec85...@syzkaller.appspotmail.com

loop0: detected capacity change from 0 to 128
EXT4-fs (loop0): mounted filesystem without journal. Quota mode: none.
general protection fault, probably for non-canonical address 0xdffffc0000000007: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000038-0x000000000000003f]
CPU: 0 PID: 7615 Comm: syz.0.1093 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
RIP: 0010:__ext4_journal_get_write_access+0xc3/0x6e0 fs/ext4/ext4_jbd2.c:231
Code: 31 c0 49 8d 5e 30 48 89 d8 48 c1 e8 03 42 80 3c 28 00 74 08 48 89 df e8 2b 9c b4 ff 48 8b 1b 48 83 c3 38 48 89 d8 48 c1 e8 03 <42> 80 3c 28 00 74 08 48 89 df e8 0e 9c b4 ff 4c 8b 23 4d 85 e4 4c
RSP: 0018:ffffc9000564f820 EFLAGS: 00010202
RAX: 0000000000000007 RBX: 0000000000000038 RCX: 9d50618206cb5a00
RDX: ffff88805327d940 RSI: ffffffff8a8c23a0 RDI: ffffffff8adf0f60
RBP: ffffc9000564f8f0 R08: ffff8880680abae0 R09: 0000000000000001
R10: dffffc0000000000 R11: fffffbfff1c3faee R12: ffff88807506e000
R13: dffffc0000000000 R14: ffff8880680abae0 R15: 1ffff92000ac9f0c
FS: 00007fe5743196c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f11655fff8c CR3: 0000000019e6d000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
ext4_update_primary_sb fs/ext4/ioctl.c:67 [inline]
ext4_update_superblocks_fn+0x287/0x1040 fs/ext4/ioctl.c:221
ext4_fill_super+0x2ac4/0x7dc0 fs/ext4/super.c:5706
get_tree_bdev+0x3f1/0x610 fs/super.c:1366
vfs_get_tree+0x88/0x270 fs/super.c:1573
do_new_mount+0x24a/0xa40 fs/namespace.c:3078
do_mount fs/namespace.c:3421 [inline]
__do_sys_mount fs/namespace.c:3629 [inline]
__se_sys_mount+0x2e3/0x3d0 fs/namespace.c:3606
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fe57339da0a
Code: 48 c7 c2 e8 ff ff ff f7 d8 64 89 02 b8 ff ff ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fe574318e58 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fe574318ee0 RCX: 00007fe57339da0a
RDX: 0000200000000100 RSI: 0000200000000180 RDI: 00007fe574318ea0
RBP: 0000200000000100 R08: 00007fe574318ee0 R09: 0000000002000c16
R10: 0000000002000c16 R11: 0000000000000246 R12: 0000200000000180
R13: 00007fe574318ea0 R14: 000000000000025e R15: 0000200000000280
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:__ext4_journal_get_write_access+0xc3/0x6e0 fs/ext4/ext4_jbd2.c:231
Code: 31 c0 49 8d 5e 30 48 89 d8 48 c1 e8 03 42 80 3c 28 00 74 08 48 89 df e8 2b 9c b4 ff 48 8b 1b 48 83 c3 38 48 89 d8 48 c1 e8 03 <42> 80 3c 28 00 74 08 48 89 df e8 0e 9c b4 ff 4c 8b 23 4d 85 e4 4c
RSP: 0018:ffffc9000564f820 EFLAGS: 00010202
RAX: 0000000000000007 RBX: 0000000000000038 RCX: 9d50618206cb5a00
RDX: ffff88805327d940 RSI: ffffffff8a8c23a0 RDI: ffffffff8adf0f60
RBP: ffffc9000564f8f0 R08: ffff8880680abae0 R09: 0000000000000001
R10: dffffc0000000000 R11: fffffbfff1c3faee R12: ffff88807506e000
R13: dffffc0000000000 R14: ffff8880680abae0 R15: 1ffff92000ac9f0c
FS: 00007fe5743196c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f93cede82f8 CR3: 0000000019e6d000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
0: 31 c0 xor %eax,%eax
2: 49 8d 5e 30 lea 0x30(%r14),%rbx
6: 48 89 d8 mov %rbx,%rax
9: 48 c1 e8 03 shr $0x3,%rax
d: 42 80 3c 28 00 cmpb $0x0,(%rax,%r13,1)
12: 74 08 je 0x1c
14: 48 89 df mov %rbx,%rdi
17: e8 2b 9c b4 ff call 0xffb49c47
1c: 48 8b 1b mov (%rbx),%rbx
1f: 48 83 c3 38 add $0x38,%rbx
23: 48 89 d8 mov %rbx,%rax
26: 48 c1 e8 03 shr $0x3,%rax
* 2a: 42 80 3c 28 00 cmpb $0x0,(%rax,%r13,1) <-- trapping instruction
2f: 74 08 je 0x39
31: 48 89 df mov %rbx,%rdi
34: e8 0e 9c b4 ff call 0xffb49c47
39: 4c 8b 23 mov (%rbx),%r12
3c: 4d 85 e4 test %r12,%r12
3f: 4c rex.WR


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